docs: async def _on_response_prepare(self,
                                     request: web.Request,
                                     response: web.StreamResponse):
          """Non-preflight CORS request response processor.
  
          If request is done on CORS-enabled route, process request parameters
          and set appropriate CORS response headers.
          """
          if (not self._router_adapter.is_cors_enabled_on_request(request) or
                  self._router_adapter.is_preflight_request(request)):
              # Either not CORS enabled route, or preflight request which is
              # handled in its own handler.
              return
  
          # Processing response of non-preflight CORS-enabled request.
  
          config = self._router_adapter.get_non_preflight_request_config(request)
  
          # Handle according to part 6.1 of the CORS specification.
  
          origin = request.headers.get(hdrs.ORIGIN)
          if origin is None:
              # Terminate CORS according to CORS 6.1.1.
              return
  
          options = config.get(origin, config.get("*"))
          if options is None:
              # Terminate CORS according to CORS 6.1.2.
              return
  
          assert hdrs.ACCESS_CONTROL_ALLOW_ORIGIN not in response.headers
          assert hdrs.ACCESS_CONTROL_ALLOW_CREDENTIALS not in response.headers
          assert hdrs.ACCESS_CONTROL_EXPOSE_HEADERS not in response.headers
  
          # Process according to CORS 6.1.4.
          # Set exposed headers (server headers exposed to client) before
          # setting any other headers.
          if options.expose_headers == "*":
              # Expose all headers that are set in response.
              exposed_headers = \
                  frozenset(response.headers.keys()) - _SIMPLE_RESPONSE_HEADERS
              response.headers[hdrs.ACCESS_CONTROL_EXPOSE_HEADERS] = \
                  ",".join(exposed_headers)
  
          elif options.expose_headers:
              # Expose predefined list of headers.
              response.headers[hdrs.ACCESS_CONTROL_EXPOSE_HEADERS] = \
                  ",".join(options.expose_headers)
  
          # Process according to CORS 6.1.3.
          # Set allowed origin.
          response.headers[hdrs.ACCESS_CONTROL_ALLOW_ORIGIN] = origin
          if options.allow_credentials:
              # Set allowed credentials.
              response.headers[hdrs.ACCESS_CONTROL_ALLOW_CREDENTIALS] = _TRUE